Composition for forming upper layer film for immersion exposure, upper layer film for immersion exposure, and method of forming photoresist pattern

ABSTRACT

The object of the invention is to provide a composition for forming an upper layer film for immersion exposure capable of forming an upper layer film effectively inhibited from developing defects through an immersion exposure process, such as a watermark defect and dissolution residue defect. Also provided are an upper layer film for immersion exposure and a method of forming a resist pattern. The composition for forming an upper layer film includes a resin ingredient and a solvent. The resin ingredient includes a resin (A) having at least one kind of repeating units selected among those represented by the formulae (1-1) to (1-3) and at least either of the two kinds of repeating units represented by the formulae (2-1) and (2-2). (1-1) (1-2) (1-3) (2-1) (2-2) [In the formulae, R 1  represents hydrogen or methyl; R 2  and R 3  each represents methylene, linear or branched C 2-6  alkylene, or alicyclic C 4-12  alkylene; R 4  represents hydrogen or methyl; and R 5  represents a single bond, methylene, or linear or branched C 2-6  alkylene.].

TECHNICAL FIELD

The present invention relates to a composition for forming an upperlayer film for liquid immersion exposure, an upper layer film for liquidimmersion exposure, and a method for the formation of a photoresistpattern. More specifically, the present invention relates to acomposition for forming an upper layer film which can sufficientlyprotect a photoresist in a liquid immersion lithographic process and isuseful for forming an upper layer which protects a lens of a projectionaligner by suppressing elution of a photoresist component, an upperlayer film for liquid immersion exposure, and a method for the formationof a photoresist pattern.

BACKGROUND ART

Semiconductor devices and the like are produced using a stepping orstep-and-scan projection aligner which transfers a pattern of a reticleas a photomask onto each shot region on a wafer coated with aphotoresist through a projection optical system.

The resolution of a projection optical system used in a projectionaligner increases as the exposure wavelength decreases and the numericalaperture of the projection optical system increases. Therefore, theexposure wavelength (i.e., the wavelength of radiation used in theprojection aligner) has decreased and the numerical aperture of theprojection optical system has increased year by year as integratedcircuits have been scaled down.

The depth of focus is as important as the resolution when a resist isexposed. Resolution R and depth of focus δ are expressed respectively bythe following formulae. When obtaining the same resolution R, a largerdepth of focus δ can be obtained using radiation with a shorterwavelength.

R=k ₁·λ/NA  (i)

δ=k ₂·λ/NA²  (ii)

wherein λ is an exposure wavelength, NA is a numerical aperture of theprojection optical system, and k₁ and k₂ are process coefficients.

In the above exposure technology, a photoresist film is formed on thesurface of the exposure target wafer, and the pattern is transferred tothe photoresist film. In a conventional projection aligner, the space inwhich the wafer is placed is filled with air or nitrogen.

When the space between the wafer and the lens of the projection aligneris filled with a medium having a refractive index of n, the resolution Rand the depth of focus 6 are represented by the following formulae.

R=k ₁·(λ/n)/NA  (iii)

δ=k ₂ ·nλ/NA²  (iv)

For example, when water is used as the medium in an ArF process, theresolution R is 69.4% (R=k₁·(k/1.44)/NA) and the depth of focus is 144%(6=k₂·1.44λ/NA²) as compared with the case in which air or nitrogen isused as the medium, when the refractive index of light with a wavelengthof 193 nm is n=1.44.

Such a projection exposure method in which the wavelength of radiationis reduced to transfer a more minute pattern is called liquid immersionlithography. The liquid immersion lithography is considered to be anessential technology for lithography with reduced dimensions,particularly for lithography with dimensions of several tens ofnanometers. A projection aligner used for the method is also known inthe art.

In the liquid immersion lithography using water as a medium ofimmersion, a photoresist film formed on a wafer and a lens of aprojection aligner are brought into contact with water. For this reason,water may permeate the photoresist film and decrease resolution. Inaddition, photoresist components may elute into water and pollute thesurface of the lens of the projection aligner.

A method of forming an upper layer film on a photoresist film in orderto shut out the medium such as water has been proposed (see, PatentDocument 1 for example).

[Patent Document 1] JP-A 2007-24959

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The upper layer film must exhibit sufficient transparency to thewavelength of radiation, must form a protective film on the photoresistfilm without being intermixed with the photoresist film, must maintain astable covering effect without eluting components into a medium such aswater used during liquid immersion lithography, and must be easilydissolved in an alkaline solution or the like as a developer.

Although the upper layer film commonly used in liquid immersionlithography is provided with water repellency to suppress a watermarkdefect which is a phenomenon of leaving a watermark having a size of 1μm or larger on a resist pattern by preventing water drops fromremaining on a protective film during exposure, such a film has aproblem of leaving more minute defects (dissolution residue defects witha size of 0.2 μm or smaller). The dissolution residue defects areproduced due to permeation of a small amount of water into a protectivefilm even if water is prevented from remaining on the protective film.Specifically, water permeation reduces dissolution of a photoresist filmand locally inhibits sufficient resolution of a pattern shape whichshould otherwise be resolved, resulting in pattern shape defects whichare detected as dissolution residue defects. For this reason, although aknown upper layer film in liquid immersion lithography can be expectedto effectively suppress watermark defects, such a film is stillunsatisfactory due to production of more minute dissolution residuedefects. Therefore, further improvement has been desired.

The present invention has been achieved to overcome such a problem, andhas an object of providing a composition for forming an upper layer filmused in liquid immersion lithography which can form a film possessingsufficient transparency to light with a short wavelength (particularly248 nm (KrF) and 193 nm (ArF)) on a photoresist film while causingalmost no intermixing with the photoresist film, can be stablymaintained without being dissolved in a medium such as water duringliquid immersion lithography, can form a high resolution resist patternwhile effectively suppressing defects such as watermark defects causedby liquid immersion lithography, and can suppress production of moreminute defects, an upper layer film in liquid immersion lithography, anda method for forming a photoresist pattern.

Means for Solving the Problems

The present invention is as follows.

[1] A composition for forming an upper layer film in liquid immersionlithography including a resin component and a solvent, characterized inthat the resin component includes a resin (A) having at least onerepeating unit selected from a repeating unit represented by thefollowing formula (1-1), a repeating unit represented by the followingformula (1-2), and a repeating unit represented by the following formula(1-3), and at least one repeating unit selected from a repeating unitrepresented by the following formula (2-1) and a repeating unitrepresented by the following formula (2-2).

(In the general formulae (1-1) to (1-3), R′ individually is a hydrogenatom or a methyl group, R² and R³ individually are a methylene group, alinear or branched alkylene group having 2 to 6 carbon atoms, or analicyclic alkylene group having 4 to 12 carbon atoms.)

(In the general formulae (2-1) and (2-2), R⁴ individually is a hydrogenatom or a methyl group, and R⁵ individually is a single bond, amethylene group, or a linear or branched alkylene group having 2 to 6carbon atoms.)[2] The composition for forming an upper layer film in liquid immersionlithography according to [1] above, wherein the resin (A) forms a filmhaving a receding contact angle with water of less than 60°.[3] The composition for forming an upper layer film in liquid immersionlithography according to [1] or [2] above, wherein the resin componentfurther includes a resin (B) having at least one repeating unit selectedfrom a repeating unit represented by the following formula (3-1), arepeating unit represented by the following formula (3-2), and arepeating unit represented by the following formula (3-3), and arepeating unit represented by the following formula (4), the resin (B)forming a film having a receding contact angle with water of 65° ormore.

(In the general formulae (3-1) to (3-3), R⁶ individually is a hydrogenatom, a methyl group, or a trifluoromethyl group, R^(6′) is a linear orbranched alkyl group having 1 to 3 carbon atoms with at least onehydrogen atom being substituted by a fluorine atom, R⁷ individually is asingle bond, a methylene group, a linear or branched alkylene grouphaving 2 to 6 carbon atoms, or an alicyclic alkylene group having 4 to12 carbon atoms, R⁸ is a linear or branched alkyl group having 1 to 10carbon atoms with at least one hydrogen atom being substituted by afluorine atom or an alicyclic alkyl group having 3 to 10 carbon atomswith at least one hydrogen atom being substituted by a fluorine atom,and A represents a single bond, a carbonyl group, a carbonyloxy group,or an oxycarbonyl group.)

(In the general formula (4), R⁹ is a hydrogen atom, a methyl group, or atrifluoromethyl group, and R¹⁰ is a single bond, a methylene group, or alinear or branched alkylene group having 2 to 6 carbon atoms.)[4] The composition for forming an upper layer film in liquid immersionlithography according to any one of [1] to [3] above, wherein the resin(A) includes the repeating unit represented by the general formula (1-1)and the repeating unit represented by the general formula (2-1), andwherein the resin (B) includes the repeating unit represented by thegeneral formula (3-1) and the repeating unit represented by the generalformula (4-1).[5] The composition for forming an upper layer film in liquid immersionlithography according to any one of [1] to [4] above, wherein thecontent of the resin (A) is in the range from 5% to 70% by weight basedon 100% by weight of the total of the resin component.[6] An upper layer film in liquid immersion lithography characterized inthat the film is formed using the composition for forming an upper layerfilm in liquid immersion lithography according to any one of [1] to [5]above.[7] A method for forming a photoresist pattern characterized byincluding:(1) applying a photoresist composition to a substrate to form aphotoresist film;(2) applying the composition for forming an upper layer film in liquidimmersion lithography according to any one of [1] to [5] above to thephotoresist film to form an upper layer film; and(3) disposing a liquid immersion medium between the upper layer film anda lens, irradiating the photoresist film and the upper layer film withexposure light through the liquid immersion medium and a mask having aspecific pattern, and developing the photoresist film to obtain aphotoresist pattern.

EFFECT OF THE INVENTION

According to the composition for forming an upper layer film in liquidimmersion lithography (hereinafter, referred to also as “composition forforming an upper layer film”) of the present invention, the compositioncontains the resin (A) having excellent solubility in an alkalinedeveloper, and being locally present at the interface between thephotoresist film and the upper layer film, suppresses a decrease insolubility of the photoresist film in the developer and preventsdissolution residue defects due to water permeation. On the other hand,since the resin (B) with high water repellency is locally present on thesurface of the protective film, watermark defects can be effectivelyprevented. In addition, the composition can form a film possessingsufficient transparency to light with a short wavelength (particularly248 nm (KrF) and 193 nm (ArF)) on a photoresist film while causingalmost no intermixing with the photoresist film, can be stablymaintained without being dissolved in a medium such as water duringliquid immersion lithography, can form a high resolution resist patternwhile effectively suppressing defects such as watermark defects causedby liquid immersion lithography, and can suppress production of moreminute defects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing the shape of aline-and-space pattern.

FIG. 2 is an explanatory view schematically showing the manner ofplacing an 8-inch silicon wafer on a silicone rubber sheet so as toprevent leakage of ultra-pure water in the measurement of the amount ofelution from the upper layer film formed from the composition forforming an upper layer film of the present invention.

FIG. 3 is a cross-sectional view showing measurement of the amount ofelution from the upper layer film formed from the composition forforming an upper layer film of the present invention.

EXPLANATION OF THE REFERENCE NUMBERS

-   1: substrate, 2: pattern, 3: 8-inch silicon wafer, 4: hexamethyl    disilazane treated layer, 5: silicone rubber sheet, 6: center    cut-out portion, 7: super pure water, 8: lower layer antireflection    film, 9: upper layer film, 10: 8-inch silicon wafer, 11: resist    film, La: line width on the upper part of the film, Lb: line width    La on the middle of the film.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is described in further detail.

In this specification, “(meth)acryl” means acryl and methacryl.

[1] Composition for Forming Upper Layer Film in Liquid ImmersionLithography [Resin (A)]

The composition for forming an upper layer film of the present inventionincludes a resin (A) having at least one repeating unit selected from arepeating unit represented by the following general formula (1-1)(hereinafter, referred to as “repeating unit (1-1)”), a repeating unitrepresented by the following general formula (1-2) (hereinafter,referred to as “repeating unit (1-2)”), and a repeating unit representedby the following general formula (1-3) (hereinafter, referred to as“repeating unit (1-3)”).

(In the general formulae (1-1) to (1-3), R′ individually is a hydrogenatom or a methyl group, R² and R³ individually are a methylene group, alinear or branched alkylene group having 2 to 6 carbon atoms, or analicyclic alkylene group having 4 to 12 carbon atoms.)

Examples of the above-mentioned linear or branched alkylene group having2 to 6 carbon atoms for R² and R³ in the general formulae (I-1) and(1-2) include ethylene group, propylene group such as 1,3-propylenegroup and 1,2-propylene group, tetramethylene group, pentamethylenegroup, hexamethylene group, 1-methyl-1,3-propylene group,2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group,1-methyl-1,4-butylene group, 2-methyl-1,4-butylene group, ethylidenegroup, propylidene group, 2-propylidene group and the like.

Additionally, examples of the alicyclic alkylene group having 4 to 12carbon atoms for R² and R³ include a monocyclic hydrocarbon ring group,a bridged cyclic hydrocarbon ring group and the like.

Examples of the monocyclic hydrocarbon ring group include an arylenegroup such as phenylene group and tolylene group, a cycloalkylene grouphaving 4 to 12 carbon atoms including a cyclobutylene group such as1,3-cyclobutylene group, a cyclopentylene group such as1,3-cyclopentylene group, a cyclohexylene group such as1,4-cyclohexylene group, a cyclooctylene group such as 1,5-cyclooctylenegroup, and the like.

In addition, examples of the bridged cyclic hydrocarbon ring groupinclude a bi-cyclic to tetra-cyclic hydrocarbon ring group having 4 to12 carbon atoms including a norbornylene group such as 1,4-norbornylenegroup and 2,5-norbornylene group, an adamantylene group such as1,5-adamantylene group and 2,6-adamantylene group, and the like.

Examples of the monomer for forming the above-mentioned repeating unit(1-1) include 2-methacryloyloxyethyl hexahydrophthalate,3-methacryloyloxypropyl hexahydrophthalate, 4-methacryloyloxybutylhexahydrophthalate and the like.

Additionally, examples of the monomer for forming the above-mentionedrepeating unit (1-2) include 2-methacryloyloxy cyclohexacarboxylate,3-methacryloyloxy propylcarboxylate, and the like.

Further, examples of the monomer for forming the above-mentionedrepeating unit (1-3) include (meth)acrylic acid.

The resin (A) further contains at least one repeating unit of arepeating unit represented by the following general formula (2-1)(hereinafter, referred to as “repeating unit (2-1)”) and a repeatingunit represented by the following general formula (2-2) (hereinafter,referred to as “repeating unit (2-2)”). At the interface between anunexposed photoresist film and a protective film, the protective film isdissolved in a developer during development, while the photoresist filmis dispersed without being dissolved in the developer. As a result, thephotoresist film component resin dispersed in the developer during arinse process after development re-adheres to the photoresist film. Whenthe repeating units (2-1) and (2-2) having strongly acidic groups areused, re-adhesion of the resin (BLOB defects; defect size: 0.2 μm orlarger) after the rinse process can be prevented since the resin in thephotoresist film is deprotected and dissolved in the developer.

(In the general formulae (2-1) and (2-2), R⁴ individually is a hydrogenatom or a methyl group, and R⁵ individually is a single bond, amethylene group, or a linear or branched alkylene group having 2 to 6carbon atoms.)

Description for R² in the above-mentioned general formula (1-1) appliesto the linear or branched alkylene group having 2 to 6 carbon atoms forR⁵ in the above-mentioned general formulae (2-1) and (2-2).

Additionally, examples of the monomer for the formation of theabove-mentioned general formulae (2-1) and (2-2) include vinyl sulfonicacid, allyl sulfonic acid, 2-acrylamide-2-methyl-1-propane sulfonicacid, 4-vinyl-1-benzene sulfonic acid and the like.

For the above-mentioned the resin (A), there are no particularlimitations to the combination of at least one of the repeating units(1-1) to (1-3) and at least one of the repeating units (2-1) and (2-2).

A combination of the repeating unit (1-1) and the repeating unit (2-1)is particularly preferred. In the case of this combination, re-adhesionof the resin after the rinse process can be prevented since the resin inthe photoresist film is deprotected and dissolved in the developer.

In addition, the receding contact angle with water of the film formedfrom the resin (A) is preferably less than 60°, and more preferably lessthan 40°. The term “receding contact angle of a film with water” refersto a contact angle with water of a film having a thickness of 90 nmwhich is formed by spin-coating a 4-methyl-2-pentanol solution of theresin (A) on an 8-inch silicon wafer, and baking (PB) at a temperatureof 90° C. for 60 seconds on a hot plate. The “receding contact angle” inthe present specification refers to a contact angle between a liquidsurface and a substrate on which the above-mentioned film is formed,when 25 μL of water is dropped on the substrate and thereafter suctionedat a rate of 10 μL/min. The receding contact angle can be measured using“DSA-10” manufactured by KRUS as described later in Examples.

[Resin (B)]

It is preferable in the present invention to further contain a resin (B)having at least one repeating unit selected from a repeating unitrepresented by the following formula (3-1) (hereinafter, referred to as“repeating unit (3-1)”), a repeating unit represented by the followingformula (3-2) (hereinafter, referred to as “repeating unit (3-2)”), anda repeating unit represented by the following formula (3-3)(hereinafter, referred to as “repeating unit (3-3)”), and a repeatingunit represented by the following formula (4) (hereinafter, referred toas “repeating unit (4)”), and capable of forming a film having areceding contact angle with water of 65° or more.

(In the general formulae (3-1) to (3-3), R⁶ individually is a hydrogenatom, a methyl group, or a trifluoromethyl group, R^(6′) is a linear orbranched alkyl group having 1 to 3 carbon atoms with at least onehydrogen atom being substituted by a fluorine atom, R⁷ individually is asingle bond, a methylene group, a linear or branched alkylene grouphaving 2 to 6 carbon atoms, or an alicyclic alkylene group having 4 to12 carbon atoms, R⁸ is a linear or branched alkyl group having 1 to 10carbon atoms with at least one hydrogen atom being substituted by afluorine atom or an alicyclic alkyl group having 3 to 10 carbon atomswith at least one hydrogen atom being substituted by a fluorine atom,and A represents a single bond, a carbonyl group, a carbonyloxy group,or an oxycarbonyl group.)

(In the general formula (4), R⁹ is a hydrogen atom, a methyl group, or atrifluoromethyl group, and R¹⁰ is a single bond, a methylene group, or alinear or branched alkylene group having 2 to 6 carbon atoms.)

Examples of the above-mentioned linear or branched alkyl group having 1to 3 carbon atoms with at least one hydrogen atom being substituted by afluorine atom for R^(6′) in the general formula (3-2) include an alkylgroup such as methyl group, ethyl group, propyl group and isopropylgroup with at least one hydrogen atom being substituted by a fluorineatom, and the like.

In addition, description for R² in the above-mentioned general formula(1-1) applies to the linear or branched alkylene group having 2 to 6carbon atoms and the alicyclic alkylene group having 4 to 12 carbonatoms for R⁷ in the above-mentioned general formulae (3-1) to (3-3).

Moreover, examples of the above-mentioned linear or branched alkyl grouphaving 1 to 10 carbon atoms with at least one hydrogen atom beingsubstituted by a fluorine atom for R⁸ in the general formula (3-3)include an alkyl group such as methyl group, ethyl group, propyl group,isopropyl group, butyl group, isobutyl group, sec-butyl group,tert-butyl group, pentyl group, isopentyl group, neopentyl group, hexylgroup, heptyl group, octyl group, nonyl group and decyl group with atleast one hydrogen atom being substituted by a fluorine atom, and thelike.

Furthermore, examples of the above-mentioned cycloalkyl group having 3to 10 carbon atoms with at least one hydrogen atom being substituted bya fluorine atom for R⁸ include an alicyclic alkyl group such ascyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexylgroup, cycloheptyl group, cyclooctyl group, cyclononyl group andcyclodecyl group with at least one hydrogen atom being substituted by afluorine atom, and the like.

Examples of the monomer for forming the above-mentioned repeating unit(3-1) include (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-3-propyl)(meth)acrylate, (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-butyl)(meth)acrylate, (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-5-pentyl)(meth)acrylate, (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)(meth)acrylate,2-[[5-(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]bicyclo[2.2.1]heptyl](meth)acrylate,3-[[8-(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecyl](meth)acrylateand the like.

Additionally, examples of the monomer for the formation of theabove-mentioned repeating unit (3-2) include (monofluoromethyl)acrylate,(difluoromethyl)acrylate, (trifluoromethyl)acrylate,(monofluoroethyl)acrylate, (difluoroethyl)acrylate,(trifluoroethyl)acrylate, (tetrafluoroethyl)acrylate,(pentafluoroethyl)acrylate, and the like.

Further, examples of the monomer for the formation of theabove-mentioned repeating unit (3-3) include[[(trifluoromethyl)sulfonyl]amino]ethyl-1-methacrylate,2-[[(trifluoromethyl)sulfonyl]amino]ethyl-1-acrylate, a compoundrepresented by the following formulae, and the like.

Additionally, description for R² in the above-mentioned general formula(1-1) applies to the linear or branched alkylene group having 2 to 6carbon atoms for R¹⁰ in the above-mentioned general formula (4).

Examples of the monomer for formation of the above-mentioned repeatingunit (4) include vinyl sulfonic acid, allyl sulfonic acid,2-acrylamide-2-methyl-1-propane sulfonic acid, 4-vinyl-1-benzenesulfonic acid and the like.

For the above-mentioned resin (B), there are no particular limitationsto the combination of at least one of the repeating units (3-1) to (3-3)and the repeating unit (4).

A combination of the repeating unit (3-1) and the repeating unit (4) isparticularly preferred. In the case of this combination, the high waterrepellency can prevent watermark defects due to water drop residue.

Additionally, the above-mentioned resin (B) is a resin having a recedingcontact angle of the film formed from the resin (B) with water ofpreferably 65° or more, and more preferably 69° or more. The term“receding contact angle of a film with water” refers to a contact anglewith water of a film having a thickness of 90 nm which is formed byspin-coating a 4-methyl-2-pentanol solution of the resin (B) on an8-inch silicon wafer, and baking (PB) at a temperature of 90° C. for 60seconds on a hot plate.

In the case of containing the resin (B), the receding contact angle ofthe resin (A) with water may be lower than the receding contact angle of65° or more of the resin (B) which has high water repellency. Therefore,the resin (B) can be caused to be locally present on the resin (A) in amixture of the resin (A) and the resin (B), whereby it is possible tohave their respective functions be shared. Specifically, the resin (B)having high water repellency which is caused to be locally present inthe upper part of the upper layer film can maintain high recedingcontact angle of the resin mixture even if blended with the resin (A),whereby watermark defects due to water drop residue can be prevented. Inaddition, since the resin (A) has excellent solubility in an alkalinedeveloper, local presence of the resin (A) in the lower part of theresin (B) (interface of the resist film and the upper layer film forliquid immersion) suppresses a decrease of solubility of the intermixinglayer, thereby decreasing dissolution residue defects. For this reason,in addition to watermark defects, dissolution residue defects can beprevented.

[Other Resins]

In addition to the above-mentioned resin (A) and resin (B), thecomposition of the present invention may contain other resin(hereinafter, referred to as “other resin (C)”).

Examples of the above-mentioned other resin (C) include a copolymer of(1,1,1,3,3,3-hexafluoro-2-propyl)methacrylate and(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylate, acopolymer of (2,2,2-trifluoroethyl)methacrylate and(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylate, andthe like. These other resins (C) may be used singly or in combination oftwo or more types thereof.

In the case of containing the other resin (C) as the resin component,not only blob defects can be reduced, but also a receding contact angleof 72° or more which brings about high water repellency can be ensured.

The content of the above-mentioned resin (A) is preferably in the rangefrom 5% to 70% by weight, and more preferably from 10% to 50% by weightbased on 100% by weight of the total of the resin component. When thecontent is less than 5% by weight, a sufficient effect of preventingdissolution residue defects may not be obtained. On the other hand, whenthe content is more than 70% by weight, a high receding contact angle ofthe resin (B) having water repellency may not be maintained.

Additionally, the content of the above-mentioned resin (B) is preferablyin the range from 20% to 95% by weight, and more preferably from 50% to95% by weight based on 100% by weight of the total of the resincomponent. When the content is less than 20% by weight, a high recedingcontact angle of 69° cannot be maintained On the other hand, when thecontent is more than 95% by weight, blob defects cannot be reduced.

Further, the content of the above-mentioned resin (C) is preferably inthe range from 3% to 50% by weight, and more preferably from 3% to 10%based on 100% by weight of the total of the resin component. When thecontent is in the range from 3% to 50% by weight, a receding contactangle of 72° or more can be maintained.

Although the method for preparing the resins contained as theabove-mentioned resin component is not particularly limited, such resinscan be prepared by radical polymerization of one or more radicallypolymerizable corresponding monomers in a polymerization solvent in thepresence of an appropriately selected initiator and chain transferagent.

Examples of the above-mentioned polymerization solvent include analcohol such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,2-butanol, ethylene glycol, diethylene glycol and propylene glycol; acyclic ether such as tetrahydrofurane and dioxane; an alkyl ether of apolyhydric alcohol such as ethylene glycol mono methyl ether, ethyleneglycol mono ethyl ether, ethylene glycol dimethyl ether, ethylene glycoldiethyl ether, diethylene glycol mono methyl ether, diethylene glycolmono ethyl ether, diethylene glycol dimethyl ether, diethylene glycoldiethyl ether, diethylene glycol ethyl methyl ether, propylene glycolmono methyl ether and propylene glycol mono ethyl ether; an alkyl etheracetate of a polyhydric alcohol such as ethylene glycol ethyl etheracetate, diethylene glycol ethyl ether acetate, propylene glycol ethylether acetate and propylene glycol mono methyl ether acetate; anaromatic hydrocarbon such as toluene and xylene; a ketone such asacetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,4-hydroxy-4-methyl-2-pentanone and diacetone alcohol; and an ester suchas ethyl acetate, butyl acetate, methyl 2-hydroxypropionate, ethyl2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethylethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate,methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl3-ethoxypropionate and methyl 3-ethoxypropionate. Among these, a cyclicether, a ketone, an ester and the like are preferable. These solventsmay be used singly or in combination of two or more types thereof.

The weight average molecular weight (hereinafter, referred to also as“Mw”) of each resin contained as the resin component is preferably inthe range from 2,000 to 100,000, more preferably from 2,500 to 50,000,and further preferably from 3,000 to 20,000. When the Mw is less than2,000, water resistance and mechanical characteristics as an upper layerfilm may be unduly reduced. On the other hand, when the Mw is more than100,000, solubility in the above-mentioned solvent may be significantlydecreased.

Additionally, the ratio (Mw/Mn) of the Mw to the number averagemolecular weight (hereinafter, referred to also as “Mn”) for each resinis preferably in the range from 1 to 5, and more preferably from 1 to 3.The weight average molecular weight and the number average molecularweight herein refer to polystyrene-reduced values determined by gelpermeation chromatography (GPC).

It is preferable for the resin such as the resin (A) and resin (B) tocontain impurities such as halogens and metals in an amount as small aspossible. Applicability as an upper layer film and uniform solubility inan alkaline developer can be improved by reducing the amount ofimpurities.

Further, examples of the method for purification of the resin such asthe resin (A) and resin (B) include a chemical purification methodincluding washing with water, liquid-liquid extraction and the like; acombining method of a chemical purification method and a physicalpurification method including ultrafiltration, centrifugation and thelike; and the like.

The resin such as the resin (A) and resin (B) must not only form anupper layer film (protective film) which is stable in a liquid immersionmedium such as water used while irradiating radiation, but also must bedissolved in a developer used for forming a resist pattern. The term“stable in a liquid immersion medium” refers to the properties of aresin showing a film thickness change determined by the “stabilityevaluation test” shown below of 3% or less of the initial thickness.

<Stability Evaluation Test>

(i) Apply a composition for forming an upper layer film (solutionprepared by dissolving a resin component in a solvent) to an 8-inchsilicon wafer by spin-coating with a coater/developer (1) “CLEAN TRACKACTS” (type name) manufactured by Tokyo Electron limited, and prebake(PB) the coating at a temperature of 90° C. for 60 seconds to form anupper layer film having a thickness of 90 nm. Measure the initialthickness of the resulting upper layer film using an opticalinterference thickness meter “LAMBDA ACE VM-2010” (type name)manufactured by Dainippon Screen Mfg. Co., Ltd.(ii) Inject ultra-pure water for 60 seconds from a rinse nozzle of thecoater/developer (1) onto the surface of the wafer on which the upperlayer film has been formed, followed by spin-drying at 4,000 rpm for 15seconds. Measure the thickness of the resulting upper layer film againto determine the thickness change (thickness reduction) of the upperlayer film. A film exhibiting a thickness reduction of 3% or less of theinitial thickness is evaluated to be “stable in a liquid immersionmedium”.

The term “soluble in a developer after forming a resist pattern” usedherein refers to the capability of an upper layer film of being removedwithout leaving a residue observable with the naked eye on the surfaceof a resist pattern after development using an alkaline aqueoussolution. That is, the resin component such as the resin (A) and resin(B) included in the composition for forming an upper layer film of thepresent invention is an alkali-soluble resin which is scarcely dissolvedin a medium such as water, but is dissolved in an alkaline aqueoussolution during development using the alkaline aqueous solution afterirradiation.

The upper layer film formed by the composition for forming an upperlayer film containing such a resin component can prevent a photoresistfilm from directly coming in contact with a medium such as water duringliquid immersion exposure, prevents deterioration of lithographicperformance of the photoresist film due to penetration of the medium,and protects the lens of the projection aligner from being polluted withcomponents eluted from the photoresist film.

The weight ratio (resin (A)/resin (B)) between the resin (A) and theresin (B) is preferably 0.05 or more, more preferably in the range from0.05 to 2.33, and further preferably from 0.10 to 1.00. When the weightratio is less than 0.05, a sufficient effect on dissolution residuedefects may not be obtained. On the other hand, when the weight ratioexceeds 2.33, it becomes impossible to maintain the receding contactangle of the resin (B) which has high water repellency. There is also apossibility that the upper layer film cannot withstand a high scanningspeed.

In addition, the composition for forming an upper layer film of thepresent invention further includes a solvent to dissolve the resin suchas the resin (A) and resin (B).

A solvent exhibiting almost no adverse effect on the lithographicperformance such as intermixing with the photoresist film when appliedto the photoresist film can be preferably used.

Examples of the solvent include a monohydric alcohol, a polyhydricalcohol, an alkyl ether of a polyhydric alcohol, an alkyl ether acetateof a polyhydric alcohol, an ether, a cyclic ether, a higher hydrocarbon,an aromatic hydrocarbon, a ketone, an ester, water, and the like.

Examples of the above-mentioned monohydric alcohol include a monohydricalcohol having 4 to 10 carbon atoms such as 1-butyl alcohol, 2-butylalcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol,3-pentanol, tert-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol,3-methyl-1-butanol, 3-methyl-1-pentanol, cyclopentanol, 1-hexanol,2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol,3,3-dimethyl-2-butanol, 2-diethyl-1-butanol, 2-methyl-1-pentanol,2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol,3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol,4-methyl-2-pentanol, 4-methyl-3-pentanol and cyclohexanol.

Examples of the above-mentioned polyhydric alcohol include ethyleneglycol, propylene glycol and the like.

Examples of the above-mentioned alkyl ether of a polyhydric alcoholinclude ethylene glycol mono methyl ether, ethylene glycol mono ethylether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether,diethylene glycol mono methyl ether, diethylene glycol mono ethyl ether,diethylene glycol dimethyl ether, diethylene glycol diethyl ether,diethylene glycol ethyl methyl ether, propylene glycol mono methylether, propylene glycol mono ethyl ether and the like.

Examples of the above-mentioned alkyl ether acetate of a polyhydricalcohol include ethylene glycol ethyl ether acetate, diethylene glycolethyl ether acetate, propylene glycol ethyl ether acetate, propyleneglycol mono methyl ether acetate and the like.

Examples of the above-mentioned ether include dipropyl ether,diisopropyl ether, butyl methyl ether, butyl ethyl ether, butyl propylether, dibutyl ether, diisobutyl ether, tert-butyl methyl ether,tert-butyl ethyl ether, tert-butyl propyl ether, di-tert-butyl ether,dipentyl ether, diisoamyl ether, cyclopentyl methyl ether, cyclohexylmethyl ether, cyclopentyl ethyl ether, cyclohexyl ethyl ether,cyclopentyl propyl ether, cyclopentyl 2-propyl ether, cyclohexyl propylether, cyclohexyl 2-propyl ether, cyclopentyl butyl ether, cyclopentyltert-butyl ether, cyclohexyl butyl ether, cyclohexyl tert-butyl etherand the like.

Examples of the above-mentioned cyclic ether include tetrahydrofurane,dioxane and the like.

Examples of the above-mentioned higher hydrocarbon include decane,dodecane, undecane and the like.

Examples of the above-mentioned aromatic hydrocarbon include benzene,toluene, xylene and the like.

Examples of the above-mentioned ketone include acetone, methyl ethylketone, methyl isobutyl ketone, cyclohexanone,4-hydroxy-4-methyl-2-pentanone, diacetone alcohol and the like.

Examples of the above-mentioned ester include ethyl acetate, butylacetate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate,ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethylhydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl3-methoxypropionate, ethyl 3-methoxypropionate, ethyl3-ethoxypropionate, methyl 3-ethoxypropionate and the like.

Among these solvents, a monohydric alcohol, an ether, a cyclic ether, analkyl ether of a polyhydric alcohol, an alkyl ether acetate of apolyhydric alcohol and a higher hydrocarbon are preferable.Particularly, a solvent containing an alcohol having 4 to 10 carbonatoms and/or an alkyl ether including an alkyl chain having 4 to 10carbon atoms is preferred.

Additionally, a surfactant may be further incorporated into thecomposition for forming an upper layer film of the present invention forthe purpose of improving the coatability, defoamability, levelingperformance and the like.

As the above-mentioned surfactant, a fluorine-based surfactant includingcommercial products such as “BM-1000” and “BM-1100” manufactured byBM-Chemie, “Megafak F142D”, “Megafak F172”, “Megafak F173” and “MegafakF183” manufactured by Dainippon ink and chemicals Inc., “FluoradFC-135”, “Fluorad FC-170C”, “Fluorad FC-430” and “Fluorad FC-431”manufactured by Sumitomo 3M Ltd., “Surfron S-112”, “Surfron S-113”,“Surfron S-131” and “Surfron S-141” manufactured by Asahi glass Co.,Ltd., “SH-28PA”, “SH-190”, “SH-193”, “SZ-6032” and “SF8428” manufacturedby Dow Corning Toray Co., Ltd., and “EMULGEN A-60”, “EMULGEN 104P” and“EMULGEN 306P” manufactured by Kao Corp. can be used. The surfactant maybe used singly or in combination of two or more types thereof.

The formulating amount of the surfactant is preferably 5 parts or lessby weight based on 100 parts by weight of the total of the resin (A) andresin (B).

The composition for forming an upper layer film can be prepared byfiltering a solution of which the total solid content has been adjustedto become a desired value through a filter with a pore size of about 200nm. The solid content is not particularly limited and may be controlledas necessary. The solid content of the composition for forming an upperlayer film is usually in the range from 0.1% to 20% by weight.

[2] Upper Layer Film in Liquid Immersion Lithography

The upper layer film in liquid immersion lithography of the presentinvention (hereinafter, referred to also as “upper layer film”) ischaracterized in that the film is made from a composition for forming anupper layer film in liquid immersion lithography. Since this upper layerfilm can effectively suppress defects inherent to liquid immersionlithography such as watermark defects and dissolution residue defects,the film can be suitably used in liquid immersion lithography. The abovedescription can be applied to the “composition for forming an upperlayer film in liquid immersion lithography”.

The upper layer film in liquid immersion lithography may be formed byapplying the above-mentioned composition for forming an upper layer filmin liquid immersion lithography to a target such as a resist film usinga known coating method such as rotational coating, cast coating and rollcoating. When the upper layer film is formed, the applied compositionmay be prebaked (hereinafter, referred to also as “PB”) in order tovaporize the solvent.

The thickness of the upper layer film is not particularly limited andmay be variously changed as required.

[3] Method for Forming Photoresist Pattern

The method for forming a photoresist pattern using the composition forforming an upper layer film of the present invention may include (1)applying a photoresist composition to a substrate to form a photoresistfilm [step (1)], (2) applying the composition for forming an upper layerfilm in liquid immersion lithography to the photoresist film to obtainan upper layer film [step (2)], and (3) disposing a liquid immersionmedium between the upper layer film and a lens, irradiating thephotoresist film and the upper layer film with exposure light throughthe liquid immersion medium and a mask having a specific pattern, anddeveloping the photoresist film to obtain a photoresist pattern [step(3)].

According to this method, an upper layer film having sufficienttransparency to a short exposure wavelength (particularly 248 nm (KrF)and 193 nm (ArF)), and causing almost no intermixing with a photoresistfilm can be formed on the photoresist film. It is also possible to forma high resolution resist pattern having a stable film of which thecomponents are extremely difficult to elute in an immersion medium suchas water during liquid immersion lithography.

The above-mentioned step (1) is a process in which a photoresistcomposition is applied to a substrate to form a photoresist film.

The above-mentioned substrate may be a silicon wafer, a silicon wafercoated with aluminum, and the like. In one preferred embodiment, anorganic or inorganic antireflection film is previously formed on thesurface of the substrate in order to bring out the potential of thephotoresist film to the maximum extent (See, for example JP-B H6-12452).

There are no particular limitations to the type of substance on whichthe photoresist film is formed. The substance may be suitably selectedfrom those generally used for forming photoresist films according to thepurpose of use of the resist, provided that a chemically amplifiedresist material containing an acid generator, particularly apositive-tone resist material, is preferably used.

Examples of the chemically amplified positive-tone resist materialinclude a photosensitive resin composition containing an alkali-solubleresin modified with an acid-dissociable group and an acid generator asessential components, and the like. Such a resin composition generatesan acid from the acid generator by irradiation (exposure). Anacid-dissociable group which protects an acidic group (such as acarboxyl group) of the resin is dissociated by the action of thegenerated acid and the acidic group is caused to be exposed. As a resultof exposure of an acidic group, the area on the resist exposed toradiation acquires increased alkali solubility and is dissolved in analkaline developer, and removed to form a positive-tone resist pattern.

Additionally, when the photoresist composition contains anacid-dissociable group-containing resin and an acid generator, it ispreferable that the above-mentioned resin has an acid-dissociablegroup-containing repeating unit in an amount of 40% to 60% by mol basedon the total amount of the repeating units of the resin. When thecontent of the repeating unit is less than 40% by mol, resolution as aresist may be impaired. When the content of this repeating unit is morethan 60% by mo %, the thickness of the resist after removing the upperlayer film may be unduly reduced.

Examples of the resin include (i) a resin having the following repeatingunit (M-1), the following repeating unit (M-2), and the followingrepeating unit (M-3); (ii) a resin having the following repeating unit(M-1), the following repeating unit (M-2), and the following repeatingunit (M-4); and (iii) a resin having the following repeating unit (M-1),the following repeating unit (M-3), and the following repeating unit(M-5); and the like.

In addition, the acid generator is a compound which generates an acidupon irradiation (exposure). The generated acid dissociates anacid-dissociable group which has been protecting an acidic group such ascarboxyl group in the resin to expose the acidic group.

Examples of the acid generator include triphenylsulfoniumnonafluoro-n-butanesulfonate, 4-cyclohexylphenyl diphenylsulfoniumnonafluoro-n-butanesulfonate,1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiopheniumnonafluoro-n-butanesulfonate, triphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,1-(4-n-butoxynaphthyl)tetrahydrothiophenium 2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,triphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate, and the like.

The acid generator may be used singly or in combination of two or moretypes thereof.

The above-mentioned photoresist composition solution (coating solution)can be prepared by adding a solvent to a resin component which forms aphotoresist film to make a solution with a solid content of 0.2% to 20%by weight and filtering the solution through a filter having a pore sizeof about 30 nm. The coating solution may be prepared by a user or acommercially available resist solution may be used.

The photoresist film may be formed by applying the coating solution ontoa substrate using a generally known coating method such as spin coating,cast coating and roll coating. When the photoresist film is formed, theapplied coating solution may be prebaked (hereinafter, referred to as“PB”) in order to vaporize the solvent.

The above-mentioned step (2) is a process in which the composition forforming an upper layer film is coated onto the surface of thephotoresist film formed in the above-mentioned step (1) and the coatedfilm is preferably baked again to form an upper layer film. The abovedescription can be applied as is to the “composition for forming anupper layer film”.

When the upper layer film is formed in this manner, it is possible toprevent direct contact of a photoresist film with a medium used forliquid immersion exposure, whereby deterioration of lithographicperformance of the photoresist film due to penetration of the medium andpollution of a lens of the projection aligner with components elutedfrom the photoresist film can be prevented.

Additionally, the thickness of the upper layer film is preferably asclose as possible to an anisoploid of λ/4m (wherein λ is a wavelength ofradiation and m is a refractive index of the protective film) since thecloser the thickness to the anisoploid of λ/4m, the greater theantireflection effect on the upper side surface of the photoresist film.

The above-mentioned step (3) is a process in which a liquid immersionmedium is disposed between the upper layer film and a lens, thephotoresist film and the upper layer film are subjected to irradiationwith exposure light through the liquid immersion medium and a maskhaving a specific pattern, and the photoresist film is subjected todevelopment to obtain a resist pattern.

The immersion medium is usually a liquid having a refractive indexhigher than air. Water is preferably used, with ultra-pure water beingparticularly preferable. The pH of the immersion liquid may be adjustedas required.

When the exposure in liquid immersion lithography is carried out, thephotoresist film is exposed through a mask having a specified pattern ina condition in which a liquid medium is filled between the lens of thephotolithography machine and the photoresist film.

As the radiation used for the liquid immersion lithography, varioustypes of radiation such as visible light; ultraviolet rays such asg-line and i-line; deep ultraviolet rays such as an excimer laser light;X-rays such as synchrotron radiation; and charged particle rays such aselectron beams may be appropriately selected according to thephotoresist film and the type of upper layer film. Among these, an ArFexcimer laser (wavelength; 193 nm) and a KrF excimer laser (wavelength;248 nm) are preferably used.

The exposure conditions such as an amount of radiation are appropriatelydetermined according to the composition of the radiation-sensitive resincomposition, types of additives, and the like.

Additionally, In order to improve the resolution, pattern shape,developability and the like of the photoresist film, it is preferredthat baking (PEB) is performed after the exposure. The bakingtemperature therefor is appropriately adjusted in accordance with theradiation-sensitive resin composition, and others. The temperature isusually in the range from 30° C. to 200° C., and preferably from 50° C.to 150° C.

After exposure or PEB, the photoresist is developed and washed asrequired, to form a desired photoresist pattern.

The upper layer film can be formed using the composition for forming anupper layer film of one embodiment of the present invention. The upperlayer film can be easily removed during development or washing after thedevelopment without separately adding a step of delaminating the upperlayer film. An alkaline developer is usually used for the development.

The above-mentioned developer is preferably used an alkaline aqueoussolution prepared by dissolving at least one an alkaline compound suchas sodium hydroxide, potassium hydroxide, sodium carbonate, sodiumsilicate, sodium metasilicate, ammonia, ethyl amine, n-propyl amine,diethyl amine, di-n-propyl amine, triethyl amine, methyl diethyl amine,dimethyl ethanol amine, triethanol amine; a tetraalkyl ammoniumhydroxide such as tetramethyl ammonium hydroxide and tetraethyl ammoniumhydroxide; pyrrole, piperidine, choline,1,8-diazabicyclo-[5.4.0]-7-undecene and1,5-diazabicyclo-[4.3.0]-5-nonane. Among these, an aqueous solution ofthe tetraalkyl ammonium hydroxide is preferably used.

Additionally, the developer may further contain an appropriate amount ofa water-soluble organic solvent such as methanol and ethanol, asurfactant and the like.

In the case of developing using the above-mentioned alkaline solution,rinsing is usually carried out after developing. Further, when drying iscarried out after developing or rinsing as required, a desiredphotoresist pattern can be obtained.

EXAMPLES

Hereinafter, the embodiments of the present invention are described indetail. In addition, “part” and “%” in the examples are based on weightunless otherwise indicated.

[1] Preparation of Radiation-Sensitive Resin Composition (α) to (γ)(1-1) Resins (α-1) to (α-3) for Radiation-Sensitive Resin Composition

Resins (α-1) to (α-3) for radiation-sensitive resin composition used toprepare a radiation-sensitive resin composition for forming aphotoresist film were synthesized as follows.

Synthesis Example 1

A monomer solution was prepared by dissolving 53.93 g (50% by mol) of acompound for forming the following repeating unit (M-1), 35.38 g (40% bymol) of a compound for forming the following repeating unit (M-2), and10.69 g (10% by mol) of a compound for forming the following repeatingunit (M-3) in 200 g of 2-butanone, and further adding 5.58 g ofdimethyl-2,2′-azobis(2-methylpropionate). On the other hand, a 500 mlthree-necked flask equipped with a thermometer and a dropping funnel wascharged with 100 g of 2-butanone and purged with nitrogen gas for 30minutes. After nitrogen purge, the content in the flask was heated to atemperature of 80° C. under stirring with a magnetic stirrer. Thepreviously prepared monomer solution was added into the flask using adropping funnel over three hours. The polymerization reaction wascarried out for six hours after initiation of dropping. After thetermination of the polymerization, the polymer solution was cooled withwater to a temperature of 30° C. or lower and was poured into 2,000 g ofmethanol. Then a white precipitate was collected by filtration and thewhite powder in a state of slurry was washed twice with 400 g ofmethanol. After that, filtration and drying at a temperature of 50° C.for 17 hours were carried out to obtain a white powdery copolymer (74 g,yield: 74%).

Mw of the copolymer was 6,900 and the ratio Mw/Mn was 1.70. As a resultof ¹³C-NMR analysis, the copolymer was found to have the repeating units(M-1), (M-2), and (M-3) in a ratio of 53.0:37.2:9.8 (% by mol), and thecontent of the repeating unit containing an acid-dissociable group was37.2% by mol. The copolymer is referred to as a resin (α-1) forradiation-sensitive resin composition.

Measurement and evaluation in Synthesis Examples were carried outaccording to the methods as follows. Those of Synthesis Examplesdescribed below are the same.

<Mw and Mn>

These were measured by gel permeation chromatography (GPC) withmonodispersed polystyrene as a standard reference material using highspeed GPC apparatus “HLC-8120” (type name) manufactured by Tosoh Corp.including GPC column (“G2000HXL”×2, “G3000HXL”×1, “G4000HXL”×1)manufactured by Tosoh Corp. under the following analysis conditions.Flow rate: 1.0 ml/min, eluate: tetrahydrofuran, column temperature: 40°C. Dispersibility Mw/Mn was calculated from the measurement result.

<¹³C-NMR Analysis>

¹³C-NMR analysis of the polymer was carried out using “JNM-EX270”manufactured by JEOL Ltd.

Synthesis Example 2

A monomer solution was prepared by dissolving 47.54 g (46% by mol) of acompound for forming the following repeating unit (M-1), 12.53 g (15% bymol) of a compound for forming the following repeating unit (M-2), and39.93 g (39% by mol) of a compound for forming the following repeatingunit (M-4) in 200 g of 2-butanone, and further adding 4.08 g of2,2′-azobis(isobutylonitrile). On the other hand, a 1,000 mlthree-necked flask equipped with a thermometer and a dropping funnel wascharged with 100 g of 2-butanone and purged with nitrogen gas for 30minutes. After nitrogen purge, the content in the flask was heated to atemperature of 80° C. under stirring with a magnetic stirrer. Thepreviously prepared monomer solution was added into the flask using adropping funnel over three hours. The polymerization reaction wascarried out for six hours after initiation of dropping. After thetermination of the polymerization, the polymer solution was cooled withwater to a temperature of 30° C. or lower and was poured into 2,000 g ofmethanol. Then a white precipitate was collected by filtration and thewhite powder in a state of slurry was washed twice with 400 g ofmethanol. After that, filtration and drying at a temperature of 50° C.for 17 hours were carried out to obtain a white powdery copolymer (73 g,yield: 73%).

Mw of the copolymer was 5,700 and the ratio Mw/Mn was 1.70. As a resultof ¹³C-NMR analysis, the copolymer was found to have the repeating units(M-1), (M-2), and (M-4) in a ratio of 51.4:14.6:34.0 (% by mol), and thecontent of the repeating unit containing an acid-dissociable group was48.6% by mol. The copolymer is referred to as a resin (α-2) forradiation-sensitive resin composition.

Synthesis Example 3

A monomer solution was prepared by dissolving 55.44 g (50% by mol) of acompound for forming the following repeating unit (M-1), 33.57 g (40% bymol) of a compound for forming the following repeating unit (M-5), and10.99 g (10% by mol) of a compound for forming the following repeatingunit (M-3) in 200 g of 2-butanone, and further adding 5.74 g ofdimethyl-2,2′-azobis(2-methylpropionate). A 500 ml three-necked flaskequipped with a thermometer and a dropping funnel was charged with 100 gof 2-butanone and purged with nitrogen gas for 30 minutes. Afternitrogen purge, the content in the flask was heated to a temperature of80° C. under stirring with a magnetic stirrer. The previously preparedmonomer solution was added into the flask using a dropping funnel overthree hours. The polymerization reaction was carried out for six hoursafter initiation of dropping. After the termination of thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.Then a white precipitate was collected by filtration and the whitepowder in a state of slurry was washed twice with 400 g of methanol.After that, filtration and drying at a temperature of 50° C. for 17hours were carried out to obtain a white powdery copolymer (72 g, yield:72%).

Mw of the copolymer was 6,400 and the ratio Mw/Mn was 1.67. As a resultof ¹³C-NMR analysis, the copolymer was found to have the repeating units(M-1), (M-5), and (M-3) in a ratio of 52.2:38.1:9.7 (% by mol), and thecontent of the repeating unit containing an acid-dissociable group was38.1% by mol. The copolymer is referred to as a resin (α-3) forradiation-sensitive resin composition.

(1-2) Preparation of Radiation-Sensitive Resin Composition (α) to (γ)

Each of the resins (α-1) to (α-3) for radiation-sensitive resincomposition synthesized as mentioned above, an acid generator (D), anacid diffusion controller (E), and a solvent (F) were mixed atproportions shown in Table 1, and the total solid content of eachmixture was adjusted to the range from 0.2% to 20% by weight. Theresulting solutions were filtered through a filter having a pore size ofabout 30 nm to prepare radiation-sensitive resin compositions (α) to(γ).

TABLE 1 Radiation-sensitive resin Resin Acid generator (D) Aciddiffusion controller (E) Solvent (F) composition Type Part Type PartType Part Type Part (α) α-1 30 D-1 4 E-1 0.83 F-1 1710 α-2 70 D-2 5 F-2730 (β) α-3 100 D-3 6.5 E-1 1.1 F-1 1400 D-4 2 F-2 600 F-3 30 (γ) α-1100 D-1 1.5 E-1 0.65 F-1 2400 D-2 6 F-3 30

Details of components other than the resins (α-1) to (α-3) contained inthe radiation-sensitive resin compositions (α) to (γ) shown in Table 1are as follows.

[Acid Generator (D)]

(D-1): triphenylsulfonium nonafluoro-n-butanesulfonate(D-2): 1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiopheniumnonafluoro-n-butanesulfonate(D-3): triphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate(D-4): 1-(4-n-butoxynaphthyl)tetrahydrothiophenium 2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate

[Acid Diffusion Controller (E)]

(E-1): (R)-(+)-(tert-butoxycarbonyl)-2-piperidinemethanol

[Solvent (F)]

(F-1): propylene glycol mono methyl ether acetate(F-2): cyclohexanone(F-3): γ-butyrolactone

[2] Preparation of Composition for Forming Upper Layer Film in LiquidImmersion Lithography

Resins (A-1) to (A-3), (B-1) and (C-1) capable of forming a film stablyin water during irradiation and of being soluble in a developer usedafter resist pattern formation were synthesized for the resins (A), (B)and (C) by the following method.

(2-1) Synthesis of Resin (A) Synthesis Example 4

50.0 g of 2-methacryloyloxyethyl hexahydrophthalate as a monomer forforming the repeating unit represented by the general formula (1-1) and3.24 g of 2,2′-azobis(methyl 2-methylpropionate) as an initiator weredissolved in 50 g of isopropanol to prepare a monomer solution.

On the other hand, a 500 ml three-necked flask equipped with athermometer and a dropping funnel was charged with 100 g of isopropanoland was purged with nitrogen gas for 30 minutes. After nitrogen purge,the content in the flask was heated to a temperature of 80° C. understirring using a magnetic stirrer.

The previously prepared monomer solution was added into the flask usingthe dropping funnel over three hours. After the addition, the reactionwas continued for a further three hours and the resultant reactionmixture was cooled to a temperature of 30° C. or lower to obtain apolymer solution. The polymer solution was poured into 2,400 g of water.The resulting precipitate was collected and was dried at roomtemperature under reduced pressure for 24 hours to obtain a resinpowder. The resin powder was dissolved in 1,000 g of methanol. Thesolution was transferred to a separating funnel to purify with 2,000 gof n-hexane and 400 g of water. A lower layer solution was collected andwas concentrated to 100 g. Then 4-methyl-2-pentanol was added to theconcentrated solution for solvent replacement to obtain a resinsolution. The solid content in the resin solution after solventreplacement with 4-methyl-2-pentanol was measured by putting 0.3 g ofthe resin solution on an aluminum dish, heating it on a hot plate at atemperature of 140° C. for one hour, weighing the weight of the resinsolution before heating and the weight of the residue after heating. Theresulting solid content was used for the preparation of an upper layerfilm forming composition solution and the calculation of the yield.

Mw of the resin contained in the resin solution was 9,760, the ratioMw/Mn was 1.31, and the yield was 50%. This resin is referred to as“resin (A-1)”.

The receding contact angle of the film formed from the resin (A-1) withwater was less than 40°.

Synthesis Example 5

46.95 g (85% by mol) of 2-methacryloyloxyethyl hexahydrophthalate as amonomer for forming the repeating unit represented by the generalformula (1-1) and 6.91 g of 2,2′-azobis(methyl-2-methylpropionate) as aninitiator were dissolved in 100 g of isopropanol to prepare a monomersolution.

On the other and, a 500 ml three-necked flask equipped with athermometer and a dropping funnel was charged with 50 g of isopropanoland was purged with nitrogen gas for 30 minutes. After nitrogen purge,the content in the flask was heated to a temperature of 80° C. understirring using a magnetic stirrer.

The previously prepared monomer solution was added to the flask usingthe dropping funnel over two hours. After the addition, the reaction wascontinued for a further one hour. Then, 10 g of an isopropanol solutionof 3.05 g (15% by mol) of vinyl sulfonic acid as a monomer for formingthe repeating unit represented by the general formula (2-1) was addeddropwise over 30 minutes. After that, the reaction was continued for afurther one hour and the resultant reaction mixture was cooled to atemperature of 30° C. or lower to a copolymer solution.

The copolymer solution was concentrated to 150 g and was transferred toa separating funnel. Then, 50 g of methanol and 600 g of n-hexane wereadded into the separating funnel to separate and purify the copolymer.After the separation, the lower layer solution was collected. The lowerlayer solution was diluted with isopropanol to 100 g, which was againtransferred to a separating funnel. After that, 50 g of methanol and 600g of n-hexane were added into the separating funnel for purification.Then, separation was carried out and a lower layer solution wascollected. 4-Methyl-2-pentanol was added to the collected lower layersolution for solvent replacement to adjust the total amount to 250 g.After the adjustment, 250 g of water was added for separation andpurification, and an upper layer solution was collected. Then4-methyl-2-pentanol was added to the collected upper layer solution forsolvent replacement to obtain a resin solution. The solid content in theresin solution after solvent replacement with 4-methyl-2-pentanol wasmeasured by putting 0.3 g of the resin solution on an aluminum dish,heating it on a hot plate at a temperature of 140° C. for one hour,weighing the weight of the resin solution before heating and the weightof the residue after heating. The resulting solid content was used forthe preparation of an upper layer film forming composition solution andthe calculation of the yield.

Mw of the resin contained in the resin solution was 11,060, the ratioMw/Mn was 1.55, and the yield was 75%. The ratio of the repeating unitderived from 2-methacryloyloxyethyl hexahydrophthalate and the repeatingunit derived from vinylsulfonic acid contained in the copolymer was 95:5(% by mol). This copolymer is referred to as “resin (A-2)”.

The receding contact angle with water of the film formed from the resin(A-2) was less than 40°.

Synthesis Example 6

48.15 g (95% by mol) of 2-methacryloyloxyethyl hexahydrophthalate and1.85 g (5% by mol) of 2-acryloylamino-2-methyl-1-propanesulfonic acid asmonomers for forming the repeating units represented by the formulae(I-1) and (2-2) and 3.28 g of 2,2′-azobis(methyl-2-methylpropionate) asan initiator were dissolved in 50 g of isopropanol to obtain a monomersolution.

On the other hand, a 500 ml three-necked flask equipped with athermometer and a dropping funnel was charged with 100 g of isopropanoland was purged with nitrogen gas for 30 minutes. After nitrogen purge,the content in the flask was heated to a temperature of 80° C. understirring using a magnetic stirrer.

The previously prepared monomer solution was added into the flask usingthe dropping funnel over three hours. After the addition, the reactionwas continued for a further three hours and the resultant reactionmixture was cooled to a temperature of 30° C. or lower to obtain apolymer solution.

Subsequently, the polymer solution was poured into 2400 g of water. Theresulting precipitate was collected and was dried at room temperatureunder reduced pressure for 24 hours to obtain a resin powder. The resinpowder was dissolved in 1,000 g of methanol. The solution wastransferred to a separating funnel to purify with 2,000 g of n-hexaneand 400 g of water. A lower layer solution was collected and wasconcentrated to 100 g. Then 4-methyl-2-pentanol was added to theconcentrated solution for solvent replacement to obtain a resinsolution. The solid content in the resin solution after solventreplacement with 4-methyl-2-pentanol was measured by putting 0.3 g ofthe resin solution on an aluminum dish, heating it on a hot plate at atemperature of 140° C. for one hour, weighing the weight of the resinsolution before heating and the weight of the residue after heating. Theresulting solid content was used for the preparation of an upper layerfilm forming composition solution and the calculation of the yield.

Mw of the resin contained in the resin solution was 9,260, the ratioMw/Mn was 1.35, and the yield was 30%. The ratio of the repeating unitderived from 2-methacryloyloxyethyl hexahydrophthalate and the repeatingunit derived from 2-acryloylamino-2-methyl-1-propanesulfonic acidcontained in the copolymer was 97:3 (% by mol). This copolymer isreferred to as “resin (A-3)”.

The receding contact angle of the film formed from the resin (A-3) withwater was less than 40°.

(2-2) Synthesis of Resin (B) Synthesis Example 7

46.95 g (85% by mol) of(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylate as amonomer for forming the repeating unit represented by the generalformula (3-1) and 6.91 g of 2,2′-azobis(methyl 2-methylpropionate) as aninitiator were dissolved in 100 g of isopropanol to obtain a monomersolution.

On the other hand, a 500 ml three-necked flask equipped with athermometer and a dropping funnel was charged with 50 g of isopropanoland was purged with nitrogen gas for 30 minutes. After nitrogen purge,the content in the flask was heated to a temperature of 80° C. understirring using a magnetic stirrer.

The previously prepared monomer solution was added to the flask usingthe dropping funnel over two hours. After the addition, the reaction wascontinued for a further one hour. Then, 10 g of an isopropanol solutioncontaining 3.05 g (15% by mol) of vinyl sulfonic acid as a monomer forforming the repeating unit represented by the general formula (4) wasadded dropwise over 30 minutes. After that, the reaction was continuedfor a further one hour and the resultant reaction mixture was cooled toa temperature of 30° C. or lower to obtain a copolymer solution.

Subsequently, the copolymer solution was concentrated to 150 g and wastransferred to a separating funnel. Then, 50 g of methanol and 600 g ofn-hexane were added into the separating funnel to separate and purifythe copolymer. After the separation, the lower layer solution wascollected. The lower layer solution was diluted with isopropanol to 100g, which was again transferred to a separating funnel. After that, 50 gof methanol and 600 g of n-hexane were added into the separating funnelfor purification. Then, separation was carried out and a lower layersolution was collected. 4-Methyl-2-pentanol was added to the collectedlower layer solution for solvent replacement to adjust the total amountto 250 g. After the adjustment, 250 g of water was added for separationand purification, and an upper layer solution was collected. Then4-methyl-2-pentanol was added to the collected upper layer solution forsolvent replacement to obtain a resin solution. The solid content in theresin solution after solvent replacement with 4-methyl-2-pentanol wasmeasured by putting 0.3 g of the resin solution on an aluminum dish,heating it on a hot plate at a temperature of 140° C. for one hour,weighing the weight of the resin solution before heating and the weightof the residue after heating. The resulting solid content was used forthe preparation of an upper layer film forming composition solution andthe calculation of the yield.

Mw of the copolymer contained in the resin solution was 9,760, the ratioMw/Mn was 1.51, and the yield was 65%. The ratio of the repeating unitderived from(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylate andthe repeating unit derived from vinylsulfonic acid contained in thecopolymer was 95:5 (% by mol). This copolymer is referred to as “resin(B-1)”.

The receding contact angle with water of the film formed from the resin(B-1) was 69.0°.

(2-3) Synthesis of Resin (C) Synthesis Example 8

A mixed solution was prepared by dissolving 25.0 g of 2,2-azobis(methyl2-methyl-isopropionate) in 25.0 g of methyl ethyl ketone.

On the other hand, a 2,000 ml three necked flask equipped with athermometer and a dropping funnel was charged with 104.6 g of(1,1,1,3,3,3-hexafluoro-2-propyl)methacrylate, 195.4 g of(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylate, and575.0 g of methyl ethyl ketone, and was purged with nitrogen gas for 30minutes. After nitrogen purge, the content of the flask was heated to atemperature of 80° C. under stirring using a magnetic stirrer.

The previously prepared mixed solution was added into the flask usingthe dropping funnel over five minutes, followed by aging for 360minutes. After that, the mixture was cooled to a temperature of 30° C.or lower to obtain a copolymer solution.

Subsequently, the copolymer solution was concentrated to 600 g and wastransferred to a separating funnel. Then, 193 g of methanol and 1,542 gof n-hexane were added into the separating funnel to separate and purifythe copolymer. After the separation, the lower layer solution wascollected. 117 g of methyl ethyl ketone and 1,870 g of n-hexane wereadded to the lower layer solution to separate and further purify thecopolymer. After the separation, the lower layer solution was againcollected. And then 93 g of methanol, 77 g of methyl ethyl ketone, and1,238 g of n-hexane were added to the lower layer solution to separateand still further purify the copolymer. After the separation, the lowerlayer solution was collected. 4-Methyl-2-pentanol was added to thecollected lower layer solution for solvent replacement and the solutionwas washed with distilled water. Then, 4-methyl-2-pentanol was addedagain for solvent replacement to obtain a resin solution. The solidcontent in the resin solution after solvent replacement with4-methyl-2-pentanol was measured by putting 0.3 g of the resin solutionon an aluminum dish, heating it on a hot plate at a temperature of 140°C. for one hour, weighing the weight of the resin solution beforeheating and the weight of the residue after heating. The resulting solidcontent was used for the preparation of an upper layer film formingcomposition solution and the calculation of the yield.

Mw of the copolymer contained in the resin solution was 10,200, theratio Mw/Mn was 1.65, and the yield was 65%. The ratio of the repeatingunit derived from (1,1,1,3,3,3-hexafluoro-2-propyl)methacrylate and therepeating unit derived from(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)methacrylatecontained in the copolymer was 39.5:60.5 (% by mol). This copolymer isreferred to as “resin (C-1)”.

The receding contact angle with water of the film formed from the resin(C-1) was 82.0°.

(2-4) Preparation of Composition for Forming Upper Layer Film in LiquidImmersion Lithography Example 1

A composition solution for forming an upper layer film of Example 1 witha solid content of 4% was prepared by mixing 20 parts of the resin (A-2)as a resin (A), 80 parts of the resin (B-1) as a resin (B), and 2,800parts of 4-methyl-2-pentanol as a solvent (alcohol having 4 to 10 carbonatoms) (“Solvent (G-1)” in Table 2), followed by stirring for two hoursand filtration through a filter having a pore size of 200 nm.

Examples 2 to 11 and Comparative Examples 1 to 4

Composition solutions for forming upper layer films of Examples 2 to 11and Comparative Examples 1 to 4 were prepared in the same manner as inExample 1 except for using the radiation-sensitive resin composition,the resin (A), resin (B) and resin (C), and the solvent (G) atproportions shown in Table 2.

TABLE 2 Radiation-sensitive Resin (A) Resin (B) Resin (C) Solvent (G)resin composition Type Part Type Part Type Part Type Part Example 1 (α)A-2 20 B-1 80 — G-1 2800 Example 2 (α) A-3 20 B-1 80 — G-1 2800 Example3 (α) A-2 10 B-1 90 — G-1 2800 Example 4 (α) A-2 50 B-1 50 — G-1 2800Example 5 (α) A-2 80 B-1 20 — G-1 2800 G-1 1680 Example 6 (α) A-2 20 B-180 — G-2 1120 Example 7 (α) A-1 20 B-1 80 — G-1 2800 Example 8 (β) A-220 B-1 80 — G-1 2800 Example 9 (γ) A-2 20 B-1 80 — G-1 2800 Example 10(α) A-1 20 B-1 77 C-1 3 G-1 1680 G-2 1120 Example 11 (α) A-1 20 B-1 73C-1 7 G-1 1993 G-2 498 Comparative Example 1 (α) — B-1 100 — G-1 2800Comparative Example 2 (α) — B-1 100 — G-1 1680 G-2 1120 ComparativeExample 3 (β) — B-1 100 — G-1 2800 Comparative Example 4 (γ) — B-1 100 —G-1 2800

[Solvent (G)]

(G-1): 4-methyl-2-pentanol(G-2) Diisoamyl ether

[3] Performance Evaluation of Examples

The upper layer films obtained using the composition solutions preparedin the Examples and Comparative Examples were evaluated for thefollowing items. The results are shown in Table 3.

(3-1) Upper Layer Film Removability

A coating (upper layer film) having a thickness of 90 nm was formedusing “CLEAN TRACK ACT8” (type name) manufactured by Tokyo Electronlimited on an 8-inch silicon wafer by spin-coating an upper layer filmforming composition and baking at a temperature of 90° C. for 60seconds. The thickness of the coating (film thickness) was measured with“LAMBDA ACE VM90” (type name) manufactured by Dainippon Screen Mfg. Co.,Ltd.

After that, paddle development (developer: 2.38% aqueous solution ofTMAH (tetramethylammonium hydroxide)) was carried out for 60 secondsusing “CLEAN TRACK ACT8” (type name). Then, the wafer was dried byspinning to observe the surface. When the development was complete withno residues being observed, the removability was judged to be “Good”.When a residue was observed, the removability was judged to be “Bad”.

(3-2) Measurement of Receding Contact Angle

A coating (upper layer film) having a thickness of 90 nm was formed onan 8-inch silicon wafer by spin-coating an upper layer film formingcomposition and PB at a temperature of 90° C. for 60 seconds. Promptlyafter formation, the receding contact angle was measured with “DSA-10”(type name) manufactured by KRUS according to the following procedure ata room temperature of 23° C. and humidity of 45% under atmosphericpressure.

After adjusting the wafer stage position of “DSA-10” (type name)manufactured by KRUS, the above wafer was set on the stage. A needle ofthe analyzer was filled with water, and its initial position wasminutely adjusted so that water drops could be formed on the wafer.After forming a 25 μl water drop on the wafer by discharging water fromthe needle, the needle was once withdrawn from the water drop and againreturned to the initial position to dispose the needle in the waterdrop. Then, the water drop was suctioned at a rate of 10 μl/min for 90seconds using the needle, while measuring the receding contact angleonce every second (90 times in total). An average of contact anglesmeasured in 20 seconds from the time when the measured value stabilizedwas calculated, and the result was taken as the receding contact angle.

(3-3) Intermixing

The capability of upper layer films to prevent intermixing wasevaluated.

A radiation-sensitive resin composition (α) was spin-coated on an 8-inchsilicon wafer which was previously treated with HMDS (100° C., 60seconds) using “CLEAN TRACK ACT8” (type name). The coating was baked(PB) on a hot plate at a temperature of 90° C. for 60 seconds to form aphotoresist film having a thickness of 120 nm. An upper layer filmforming composition was spin-coated on the photoresist film and PB at atemperature of 90° C. for 60 seconds to form a film (upper layer film)having a thickness of 90 nm. The film was dried by spinning at 4,000 rpmfor 15 seconds while injecting ultra-pure water onto the wafer from arinse nozzle of the “CLEAN TRACK ACT8” (type name).

The upper layer film was removed using “CLEAN TRACK ACT8” (type name) bypaddle development (developer: 2.38% TMAH aqueous solution) using an LDnozzle for 60 seconds. Although the upper layer film was removed by thedevelopment, the photoresist film which was not exposed remained as itis.

The thickness of the photoresist film was measured before and after thedevelopment using “LAMBDA ACE VM90” (type name) manufactured byDainippon Screen Mfg. Co., Ltd. When the thickness change was within 5%,it was judged that there was no intermixing between the photoresist filmand the upper layer film and the intermixing was evaluated as “Good”.When the thickness change was more than 5%, the intermixing wasevaluated as “Bad”.

(3-4) Amount of Elution

An 8-inch silicon wafer was previously treated with HMDS(hexamethyldisilazane) using “CLEAN TRACK ACTS” (type name) manufacturedby Tokyo Electron limited at a temperature of 100° C. for 60 seconds toprovide an 8-inch silicon wafer 3 having an HMDS-treated layer 4 asshown in FIGS. 2 and 3. A silicone rubber sheet 5 in the shape of asquare (thickness: 1.0 mm, 30 cm×30 cm) with the center cut out in acircle of diameter, 11.3 cm, manufactured by Kureha Elastomer Co., Ltd.was placed on the side of the HMDS-treated layer 4 of the 8-inch siliconwafer 3. In this instance, the center cut-out portion 6 of the siliconerubber sheet 5 was positioned at the center of the 8-inch silicon wafer3. Next, the cut-out portion 6 of the silicone rubber sheet 5 was filledwith 10 ml of ultra-pure water 7 using a 10 ml transfer pipette.

Separately from the above-mentioned 8-inch silicon wafer 3, another8-inch silicon wafer 10 having a pre-formed lower layer antireflectionfilm 8, resist film 11, and upper layer film 9 was prepared. This 8-inchsilicon wafer 10 was placed on the 8-inch silicon wafer 3 so that theupper layer film 9 was on the side of the silicone rubber sheet 5, thatis to say, in such a manner that the upper layer film 9 and theultra-pure water 7 were caused to come in contact so that there was noleakage of the ultra-pure water 7.

The above lower layer antireflection film 8, resist film 11, and upperlayer film 9 on the 8-inch silicon wafer 10 were formed as follows.

First, a composition for forming a lower layer antireflection film(trade name “ARC29A”, manufactured by Brewer Science, Inc.) was appliedusing the above-mentioned “CLEAN TRACK ACT8” so that a lower layerantireflection film having a thickness of 77 nm was formed. Next, theabove-mentioned radiation-sensitive resin composition (a) wasspin-coated on the lower layer antireflection film and baked at atemperature of 115° C. for 60 seconds using the above-mentioned “CLEANTRACK ACT8” to form a resist film 11 having a thickness of 205 nm. Afterthat, the above-mentioned composition for forming upper layer film wasapplied to the resist film 11 to form an upper layer film 9.

The upper layer film 9 and the silicone rubber sheet 5 were maintainedfor 10 seconds in the same position after the former was placed on thelatter. After this, the 8-inch silicon wafer 10 was removed and theultra-pure water 7 which was in contact with the upper layer film 9 wascollected using a glass pipette for use as a sample for analysis. Therecovery rate of the ultra-pure water 7 which had been filled in thecut-out portion 6 of the silicone rubber sheet 5 was 95% or more.

Subsequently, the collected sample for analysis (ultra-pure water) wassubjected to a measurement of LC-MS using a liquid chromatograph massspectrometer having “SERIES 1100” manufactured by AGILENT Corp. for LCsection, and “Mariner” manufactured by Perceptive Biosystems, Inc. forMS section under the following conditions to obtain the peak intensityof an anion part of the acid generator. In this instance, peakintensities of the aqueous solutions containing the radiation-sensitiveacid generator used for the radiation-sensitive resin composition (a) atconcentrations of 1 ppb, 10 ppb, and 100 ppb were measured under thesame conditions as the sample for analysis to prepare a calibrationcurve. The eluted amount was calculated from the above peak intensityusing this calibration curve. In the same manner, the peak intensitiesof aqueous solutions of the acid diffusion controller at concentrationsof 1 ppb, 10 ppb, and 100 ppb were measured under the same conditions asthe sample for analysis to prepare a calibration curve. The elutedamount of the acid diffusion controller was calculated from the abovepeak intensity using this calibration curve.

The elution amount was evaluated as “Bad” when the sum of the elutionamount of the anion part of the photoacid generator and the elutionamount of the acid diffusion controller calculated as mentioned abovewas 5.0×10⁻¹² mol/cm² or more, and as “Good” when that sum was less than5.0×10¹² mol/cm².

<Measurement Conditions>

Column: One column of “CAPCELL PAK MG” manufactured by Shiseido Co.,Ltd.

Flow rate: 0.2 ml/minSolvent: A 3:7 mixture of water and methanol with 0.1% of formic acidadded.Measurement temperature: 35° C.

(3-5) Blob Defect

An 8-inch silicon wafer was previously treated with HMDS(hexamethyldisilazane) using “CLEAN TRACK ACT8” (type name) manufacturedby Tokyo Electron limited at a temperature of 100° C. for 60 seconds. Acoating having a thickness of 120 nm was formed on an 8-inch siliconwafer by spin-coating the above-mentioned radiation-sensitive resincomposition (a) and baking (PB) on a hot plate at a temperature of 90°C. for 60 seconds. A coating (upper layer film) having a thickness of 90nm was formed on the resulting coating by spin-coating theabove-mentioned composition for forming an upper layer film and baking(PB) at a temperature of 90° C. for 60 seconds or at 110° C. for 60seconds. Then, the 8-inch silicon wafer was exposed through a grindingglass with no pattern formed thereon. The resulting 8-inch silicon waferwas used for evaluation of blob defect.

First, ultra-pure water was injected for 60 seconds from a rinse nozzleof “CLEAN TRACK ACT8” onto the upper layer film of the 8-inch siliconwafer and dried by spinning at 4,000 rpm for 15 seconds. Next, the upperlayer film was removed using the above-mentioned “CLEAN TRACK ACT8” bypaddle development using an LD nozzle for 60 seconds. A 2.38% TMAHaqueous solution was used as a developer for the paddle development.

The amount of dissolution residue of the upper layer film afterdevelopment was measured with “KLA2351” manufactured by KLA-Tencor Corp.for the blob defect. When the number of detected development peeldefects (blob defect) was 200 or less, the blob defect was evaluated as“Good”. When the number of detected development peel defects (blobdefects) was more than 200, the blob defect was evaluated as “Bad”.

(3-6) Patterning

The capability of high resolution resist pattern formation was evaluatedas follows.

First, a composition for forming a lower layer antireflection film(trade name “ARC29A”, manufactured by Brewer Science, Inc.) wasspin-coated on an 8-inch silicon wafer using the “CLEAN TRACK ACT8” andbaked at a temperature of 205° C. for 60 seconds to form a coating(lower layer antireflection film) having a thickness of 77 nm. Then, theradiation-sensitive resin composition (a) was spin-coated on the lowerlayer antireflection film and baked (PB) at a temperature of 90° C. for60 seconds to form a coating (photoresist film) having a thickness of120 nm.

Next, a coating (upper layer film) having a thickness of 90 nm wasformed on the resulting photoresist film by spin-coating the compositionfor forming an upper layer film and baking (PB) at a temperature of 90°C. for 60 seconds or at 110° C. for 60 seconds. After that, exposure wascarried out under optical conditions of NA of 0.78, sigma of 0.85, and2/3Ann using an ArF projection aligner “5306C” (type name) manufacturedby Nikon Corp. Then, ultra-pure water was injected to the wafer from arinse nozzle of the “CLEAN TRACK ACT8” (type name) and was dried byspinning at 4,000 rpm for 15 seconds. A hot plate in the “CLEAN TRACKACT8” (type name) was used for PEB at a temperature of 105° C. for 60seconds, and then paddle development (developer: 2.38% TMAH aqueoussolution) was carried out for 30 seconds using an LD nozzle.Subsequently, ultra-pure water was used for rinsing and drying wascarried out spinning at 4,000 rpm for 15 seconds. The amount of light atwhich a 1:1 line-and-space pattern (1L1S) having a line width of 90 nmwas formed through the resulting resist pattern was taken as an optimumdose. For the measurement, a scanning electron microscope “S-9380” (typename) manufactured by Hitachi High-Tech Fielding Corp. was used.

The cross-sectional form of the 90 nm line-and-space pattern wasobserved using a scanning electron microscope “S-4200” (type name)manufactured by Hitachi High-Tech Fielding Corp. FIG. 1 is across-sectional view schematically showing the line-and-space pattern.

A line width Lb in the middle of the film of a pattern 2 formed on asubstrate 1 and a line width La on the upper part of the film weremeasured. The patterning was judged as “Good” when 0.9≦La/Lb≦1.1 and as“Bad” when La/Lb<0.9 or when La/Lb>1.1.

(3-7) Dissolution Residue Defect

An 8-inch silicon wafer was previously treated with HMDS(hexamethyldisilazane) using “CLEAN TRACK ACT8” (type name) manufacturedby Tokyo Electron limited at a temperature of 100° C. for 60 seconds.The above-mentioned radiation-sensitive resin composition (a) wasspin-coated on the 8-inch silicon wafer and baking (PB) was carried outusing a hot plate at a temperature of 100° C. for 60 seconds to form acoating having a thickness of 120 nm. Then, the above-mentionedcomposition for forming an upper layer film was spin-coated onto theresulting coating and baking (PB) was carried out at a temperature of90° C. for 60 seconds or at 110° C. for 60 seconds to form a coatinghaving a thickness of 90 nm. After that, exposure was carried out underoptical conditions of NA of 0.78, sigma of 0.85, and 2/3Ann using an ArFprojection aligner “S306C” (type name) manufactured by Nikon Corp. Then,ultra-pure water was injected to the wafer from a rinse nozzle of the“CLEAN TRACK ACT8” (type name) and was dried by spinning at 4,000 rpmfor 15 seconds. A hot plate in the “CLEAN TRACK ACT8” (type name) wasused for PEB at a temperature of 105° C. for 60 seconds, and then paddledevelopment (developer: 2.38% TMAH aqueous solution) was carried out for30 seconds using an LD nozzle. Subsequently, ultra-pure water was usedfor rinsing and drying was carried out spinning at 4,000 rpm for 15seconds. A 160 nm space/3,600 nm pitch trench pattern was formed on theresulting 8-inch silicon wafer to evaluate dissolution defect.

The number of dissolution defects was measured with “KLA2351”manufactured by KLA-Tencor Corp. When the number of detected defects was10 or less, dissolution defect was evaluated as “Good”, and when it wasmore than 10, dissolution defect was evaluated as “Bad”.

(3-8) Watermark Defect

12-inch silicon wafer with an under layer antireflection film having athickness of 77 nm (“ARC29A”, manufactured by Brewer Science, Inc.) wasused as a substrate. For the formation of the under layer antireflectionfilm, “CLEAN TRACK ACT12” (type name) manufactured by Tokyo ElectronLimited was used.

A radiation-sensitive resin composition was spin-coated onto theabove-mentioned substrate using the “CLEAN TRACK ACT12” and then baking(PB) was carried out at a temperature of 115° C. for 60 seconds to forma photoresist film having a thickness of 120 nm. After that, a solutionof the composition for forming an upper layer film was spin-coated onthe photoresist film and baking (PB) was carried out at a temperature of90° C. for 60 seconds to form a coating (upper layer film) having athickness of 90 nm. Next, the upper layer film was exposed through amask pattern using an ArF excimer laser liquid immersion lithographicmachine “ASML AT1250i” manufactured by ASML under annular illuminationconditions of NA=0.85 and σ₀/σ₁=0.96/0.76. Pure water was used as animmersion liquid medium between the upper side of the resist(photoresist film) and the lens of the liquid immersion lithographicmachine. After that, baking (PB) was carried out at a temperature of115° C. for 60 seconds and development was carried out in a 2.38% TMAHaqueous solution at a temperature of 23° C. for 60 seconds. Then, apositive-tone resist pattern was formed by washing with water, anddrying. In this instance, a dose required for forming a 1:1line-and-space pattern (1L1S) having a line width of 100 nm was regardedas an optimum exposure dose, which was taken as the sensitivity. For themeasurement, a scanning electron microscope “S-9380” (type name)manufactured by Hitachi High-Tech Fielding Corp. was used.

A defect on a line-and-space pattern (1L1S) having a line width of 100nm was measured with “KLA2351” manufactured by KLA-Tencor Corp.Specifically, watermark defects by the “KLA2351” were confirmed byinspecting detected defects using a scanning electron microscope“S-9380” (type name) manufactured by Hitachi High-Tech Fielding Corp.When the number was 5 or less, the watermark defect was evaluated as“Good” and when it was more than 5, watermark defect was evaluated as“Bad”.

TABLE 3 Blob defect Patterning Dissolution defect Upper layer PBtemperature for PB temperature for PB temperature for film RecedingElution upper layer film upper layer film upper layer film Water-removability contact angle Intermixing amount 90° C. 110° C. 90° C. 110°C. 90° C. 110° C. mark Example 1 Good 69.0 Good Good Good Good Good GoodGood Good Good Example 2 Good 69.0 Good Good Good Good Good Good GoodGood Good Example 3 Good 69.0 Good Good Good Good Good Good Good GoodGood Example 4 Good 69.0 Good Good Good Good Good Good Good Good GoodExample 5 Good 55.0 Good Good Good Good Good Good Good Good Good Example6 Good 69.0 Good Good Good Good Good Good Good Good Good Example 7 Good69.0 Good Good Good Good Good Good Good Good Good Example 8 Good 69.0Good Good Good Good Good Good Good Good Good Example 9 Good 69.0 GoodGood Good Good Good Good Good Good Good Example 10 Good 72.0 Good GoodGood Good Good Good Good Good Good Example 11 Good 74.0 Good Good GoodGood Good Good Good Good Good Comparative Good 69.0 Good Good Good GoodGood Good Bad Bad Good Example 1 Comparative Good 69.0 Good Good GoodGood Good Good Bad Bad Good Example 2 Comparative Good 69.0 Good GoodGood Good Good Good Bad Bad Good Example 3 Comparative Good 69.0 GoodGood Good Good Good Good Bad Bad Good Example 4

As shown in Table 3, the upper layer films obtained by the compositionsfor an upper layer film according to Examples 1 to 11 exhibited “Good”results in removability evaluation, the receding contact angle of 69° to74°, and “Good” results in intermixing evaluation, elution evaluation,blob defect evaluation, patterning evaluation, dissolution defectevaluation, and watermark defect evaluation.

In addition, these upper layer film forming compositions according toExamples 1 to 11 were confirmed to have improved dissolution residuedefect as compared with the upper layer film forming compositionsaccording to Comparative Examples 1 to 4.

The present invention is not limited to the specific embodimentsdescribed above. Various alterations according to the object andapplications within the scope of the present invention are possible.

In addition, the following upper layer film forming compositions andupper layer films in liquid immersion lithography are included in suchalterations.

[1] A composition for forming an upper layer film in liquid immersionlithography which includes a resin component and a solvent, and ischaracterized in that the resin component includes a resin (A) having atleast one repeating unit selected from a repeating unit represented bythe following formula (1-1), a repeating unit represented by thefollowing formula (1-2), and a repeating unit represented by thefollowing formula (1-3) and forming a film having a receding contactangle with water of less than 60°.

(In the general formulae (I-1) to (1-3), R′ individually is a hydrogenatom or a methyl group, R² and R³ individually are a methylene group, alinear or branched alkylene group having 2 to 6 carbon atoms, or analicyclic alkylene group having 4 to 12 carbon atoms.)[2] The composition for forming an upper layer film in liquid immersionlithography according to [1] above, wherein the resin (A) includes atleast one repeating unit selected from a repeating unit represented bythe following general formula (2-1) and a repeating unit represented bythe following general formula (2-2).

(In the general formulae (2-1) and (2-2), R⁴ individually is a hydrogenatom or a methyl group, and R⁵ individually is a single bond, amethylene group, or a linear or branched alkylene group having 2 to 6carbon atoms.)[3] The composition for forming an upper layer film in liquid immersionlithography according to [1] or [2] above, wherein the resin componentfurther includes a resin (B) having at least one repeating unit selectedfrom a repeating unit represented by the following formula (3-1), arepeating unit represented by the following formula (3-2), and arepeating unit represented by the following formula (3-3), and arepeating unit represented by the following formula (4), the resin (B)forming a film having a receding contact angle with water of 65° ormore.

(In the general formulae (3-1) to (3-3), R⁶ individually is a hydrogenatom, a methyl group, or a trifluoromethyl group, R^(6′) is a linear orbranched alkyl group having 1 to 3 carbon atoms with at least onehydrogen atom being substituted by a fluorine atom, R⁷ individually is asingle bond, a methylene group, a linear or branched alkylene grouphaving 2 to 6 carbon atoms, or an alicyclic alkylene group having 4 to12 carbon atoms, R⁸ is a linear or branched alkyl group having 1 to 10carbon atoms with at least one hydrogen atom being substituted by afluorine atom or an alicyclic alkyl group having 3 to 10 carbon atomswith at least one hydrogen atom being substituted by a fluorine atom,and A represents a single bond, a carbonyl group, a carbonyloxy group,or an oxycarbonyl group.)

(In the general formula (4), R⁹ is a hydrogen atom, a methyl group, or atrifluoromethyl group, and R¹⁰ is a single bond, a methylene group, or alinear or branched alkylene group having 2 to 6 carbon atoms.)[4] The composition for forming an upper layer film in liquid immersionlithography according to any one of [1] to [3] above, wherein thecontent of the resin (A) is in the range from 5% to 70% by weight basedon 100% by weight of the total of the resin component.

INDUSTRIAL APPLICABILITY

Since the composition for forming an upper layer film of the presentinvention contains the resin (A) as a resin component, a photoresistfilm can be protected during liquid immersion lithography, a stable filmcan be maintained without eluting its components in a medium such aswater, defects such as watermark defects and pattern defects can beeffectively suppressed, a resist pattern can be formed having a highresolution, and an upper layer film can be formed having a sufficientlyhigh receding contact angle. The upper layer film can effectivelysuppress defects such as watermark defects in the formation of resistpatterns at a high scanning speed in the future. Therefore, thecomposition for forming an upper layer film of the present invention canform an upper layer film which can be suitably used in liquid immersionlithography and can be suitably used when manufacturing semiconductordevices which are expected to become increasingly miniaturized in thefuture.

1. A composition for forming an upper layer film in liquid immersionlithography comprising a resin component and a solvent, characterized inthat said resin component comprises a resin (A) having at least onerepeating unit selected from a repeating unit represented by thefollowing formula (1-1), a repeating unit represented by the followingformula (1-2), and a repeating unit represented by the following formula(1-3), and at least one repeating unit selected from a repeating unitrepresented by the following formula (2-1) and a repeating unitrepresented by the following formula (2-2).

(In the general formulae (1-1) to (1-3), R¹ individually is a hydrogenatom or a methyl group, R² and R³ individually are a methylene group, alinear or branched alkylene group having 2 to 6 carbon atoms, or analicyclic alkylene group having 4 to 12 carbon atoms.)

(In the general formulae (2-1) and (2-2), R⁴ individually is a hydrogenatom or a methyl group, and R⁵ individually is a single bond, amethylene group, or a linear or branched alkylene group having 2 to 6carbon atoms.)
 2. The composition for forming an upper layer film inliquid immersion lithography according to claim 1, wherein said resin(A) forms a film having a receding contact angle with water of less than60°.
 3. The composition for forming an upper layer film in liquidimmersion lithography according to claim 1, wherein said resin componentfurther comprises a resin (B) having at least one repeating unitselected from a repeating unit represented by the following formula(3-1), a repeating unit represented by the following formula (3-2), anda repeating unit represented by the following formula (3-3), and arepeating unit represented by the following formula (4), said resin (B)forming a film having a receding contact angle with water of 65° ormore.

(In the general formulae (3-1) to (3-3), R⁶ individually is a hydrogenatom, a methyl group, or a trifluoromethyl group, R^(6′) is a linear orbranched alkyl group having 1 to 3 carbon atoms with at least onehydrogen atom being substituted by a fluorine atom, R⁷ individually is asingle bond, a methylene group, a linear or branched alkylene grouphaving 2 to 6 carbon atoms, or an alicyclic alkylene group having 4 to12 carbon atoms, R⁸ is a linear or branched alkyl group having 1 to 10carbon atoms with at least one hydrogen atom being substituted by afluorine atom or an alicyclic alkyl group having 3 to 10 carbon atomswith at least one hydrogen atom being substituted by a fluorine atom,and A represents a single bond, a carbonyl group, a carbonyloxy group,or an oxycarbonyl group.)

(In the general formula (4), R⁹ is a hydrogen atom, a methyl group, or atrifluoromethyl group, and R¹⁰ is a single bond, a methylene group, or alinear or branched alkylene group having 2 to 6 carbon atoms.)
 4. Thecomposition for forming an upper layer film in liquid immersionlithography according to claim 1, wherein said resin (A) comprises saidrepeating unit represented by the general formula (1-1) and saidrepeating unit represented by the general formula (2-1), and whereinsaid resin (B) comprises said repeating unit represented by the generalformula (3-1) and said repeating unit represented by the general formula(4-1).
 5. The composition for forming an upper layer film in liquidimmersion lithography according to claim 1, wherein the content of saidresin (A) is in the range from 5% to 70% by weight based on 100% byweight of the total of said resin component.
 6. An upper layer film inliquid immersion lithography characterized in that said film is formedusing said composition for forming an upper layer film in liquidimmersion lithography according to claim
 1. 7. A method for forming aphotoresist pattern characterized by comprising: (1) applying aphotoresist composition to a substrate to form a photoresist film; (2)applying said composition for forming an upper layer film in liquidimmersion lithography according to claim 1 to said photoresist film toform an upper layer film; and (3) disposing a liquid immersion mediumbetween said upper layer film and a lens, irradiating said photoresistfilm and said upper layer film with exposure light through said liquidimmersion medium and a mask having a specific pattern, and developingsaid photoresist film to obtain a photoresist pattern.